In various regulations to the exhaust gas of automobiles, it is required to sample the exhaust gas when an automobile is running (on a chassis dynamometer) according to a predetermined run cycle. The run cycle is determined adequately regarding various actual running conditions of automobiles, and generally it includes a cold start, an idling and an acceleration.
In order to calculate various exhaust gas component parameters such as NMOG value, RAF value, etc., it is necessary to collect over one hundred kinds of data and to input the data into a predetermined calculating program. In this case, expertise for such kinds of data is necessary and the data input requires a lot of time with possible input errors.
Regulations to the exhaust gas of automobiles have been tightened year after year. Conventionally, exhaust gas of a sample automobile is sampled and stored in a predetermined run cycle and the stored gas is measured afterwards. Recently, the regulation has been changed to sample and measure the exhaust gas at each stage of the run cycle and the measured values should clear criteria values at each stage. For example, the exhaust gas regulation LA-4 of California State requires that the measured values of exhaust gas sampled at a cold start stage (CT), a steady run stage (CS) and a hot start stage (HT), as shown in FIG. 7, must clear the criteria values set for each stage. Thus the exhaust gas of the sample automobile running on a chassis dynamometer according to the pattern of FIG. 7 should be sampled at several preset time points.
Since the exhaust gas analysis needs high sensitivity and high precision, a gas chromatograph is used. In order to enhance the sensitivity of the measurement, the sampled gas should be concentrated before it is measured. It takes therefore nearly one hour to finish the measurements for the exhaust gas analysis. In many regulations on exhaust gas measurements, the ambient air (also called background gas) should be sampled at the same time as the exhaust gas. Thus it takes six hours in total to analyze the two kinds of gas (i.e., the exhaust gas and the background gas) sampled at the three stages of the LA-4 run cycle.
An important problem here is that the exhaust gas includes unstable components which may decompose when the sampled exhaust gas is left for a long time. The conventional measuring method described above requires a long time and cannot give adequate measurement results.